Aluminum oxide catalyst carrying material and process of making same



H. C. FISHER ETAL ALUMINUM OXIDEHCATA ATERIAL March 6, 1956 LYSTCARRYING M AND PROCESS OF MAKING SAME Filed June 21, 1952 R2 w. M M NH 0g H wF r YF M 5% H5 7 R m E VJ B United States Patent ALUMINUM OXIDECATALYST CARRYING MA- TERIAL AND PROCESS OF MAKING SAME Henry C. Fisherand Herbert F. G. Ueltz, Worcester, Mass., assignors to Norton Company,Worcester, Mass, a corporation of Massachusetts Application June 21,1952, Serial No. 294,784

8 Claims. (or. 23-443 This invention relates to aluminum oxide catalystcarrying material and to a process of making it.

One object of the invention is to provide aluminum oxide of very lowbulk specific gravity in particle size of 20 grit size and finer whichtherefore can be readily fluidized, thus accelerating any chemicalprocess which is promoted by a catalyst carried by the aluminum oxide.In this connection any mass of particles, can be suspended in any gasprovided the gas is forced through the mass of particles at high enoughvelocity. The smaller the particle size of the material the lower is theminimum velocity required for suspending the particles. Also the lowerthe bulk specific gravity of the mass of particles the lower is theminimum velocity required for suspending the particles. When a mass ofparticles is suspended in a gas the mass is said to be fluidized. Afluidized mass acts very much like a liquid and has an upper level whichrises when the velocity of the gas stream is increased and falls whenthe velocity of the gas stream is diminished (the gas usually movesupwardly through the mass of particles).

Another object of the invention is to provide very porous aluminum oxideof the character indicated. Another object is to provide aluminum oxidewhich is not only of low bulk specific gravityand of particle size ofabout 20 grit size and finer but which is also of high purity.

Another object is to provide'a simple, practical and inexpensive processfor producing aluminum oxide material of the nature indicated. 7

Other objects will be 'in part obvious or in'part pointed outhereinafter.

The accompanying drawings illustrate efficient apparatus for making thealuminum oxide material but our process is not limited to the use ofthis or similar apparatus. In the drawings,

Figure 1 is a side elevation of a spray gun and stand, a cross sectionof a rotatable barrel and an elevation of mechanism for rotating it;

Figure 2 is a sectional view on an enlarged scale of the spray gun.

The principal steps in our process are as follows: a water solution ofaluminum chloride, AlCls-6Hz0, is sprayed into a solution of ammonia,NH4OI-I. The spray of aluminum chloride solution should be allowed totravel a sufiicient distance before landing in the ammonia solution sothat spherical particles will be formed. The solvent in both cases ispreferably water.

The solutions react to form aluminum hydrate, Al(OH)3 and ammoniumchloride, NH4C1. The latter is soluble and goes into solution in theexcess of water, while the former is insoluble and forms a gel inparticles of spherical shape. The reaction isAlCls-6H20+3NH4OH=A1(OH)3+3NH4C1+6H20 and this reaction takes placesatisfactorily at room temperatures, e. g. at 70 F., and hot daytemperatures, e. g. 100 F., are not harmful 'nor are cold roomtemperatures, e. g. 50 F., harmful either. Furthermore the humidityconditions in the room are immaterial.

The fine particles of aluminum hydrate are now collected, dried and arefired at about 1450 C. (cone 16 firing conditions). The first result isto drive 01f the water according to the reaction Heat 2Al(OH) A1 0 31-10 The second result is to sinter the imperfectly united components ofeach particle to produce hard and reasonably strong tiny spheres ofalumina which are, however, quite porous, since they were derived fromalumina gel, which defines the physical condition of the aluminumhydrate. However, we provide aluminum chloride solution in the form of acreamy suspension of a pure metal oxide powder in the water and with thealuminum chloride. Furthermore the preferred oxide is aluminum oxide,A1203. This is a catalyst carrier and not a catalyst itself in mostreactions. But the metal oxide can be a catalyst and there areadvantages in providing metal oxide which is a catalyst in the reactionin which our product is to be used. For example, nickel oxide andvanadium oxide are catalysts in certain petroleum cracking reactions.But any water stable metal oxide can be used and all metals of whichthere are about seventy, form oxides. Furthermore at room temperaturesevery one of the seventy (more or less) metals has an oxide which is asolid at ordinary temperatures, so far as we are aware. Of these manyare water stable, and which are and which are not is known. In generalmost of the solid oxides (at ordinary temperatures) are water stable,exceptions being the oxides of alkali and alkaline earth metals.

For the aluminum chloride containing component we prefer to use asaturated (water) solution of AlCl3'6I-I2O. However, we can use aluminumchloride having water of crystallization of more or less than 6H2O andwhile it is more difficult to handle we can use anhydrous aluminumchloride, AlCla. The percentage of metal oxide of the total metal oxideplus saturated solution can vary from nothing to 65% by weight. But weprefer to use an appreciable amount of the metal oxide, to wit, from 20%to 65% by weight of the total metal oxide and saturated solution ofAlCls-6Hz0. The water of crystallization of the AlCls-GHzO merges withthe water of the ammonia solution during the first reaction. Theconcentration of ammonia in the ammonia solution should be kept at alltimes between 1% NH3 and NHs by weight and is preferably at least 26% byweight.

As an illustrative example we made some material as follows:

Example I A creamy suspension of fine Bayer process alumina (quite pure,microcrystalline and 01 particle size about 3-15 microns) and saturatedsolution of AlCla-6H2O in the proportion of by weight alumina to 40% byweight saturated water solution was made up. This was sprayed ahorizontal distance of about three feet with a drop of about two and ahalf feet into a rotating barrel containing ammonium hydroxide solution,26% by weight NHs the balance water. The rate of spraying was at abouttwo gallons an hour. The resultant particles were collected and fired ina kiln in an air atmosphere under cone 16 conditions. The resultant massconsisted of discrete tiny spheres, very porous, of practically purealumina of crystalline structure, with a bulk density of the mass ofabout pounds per cubic foot. This is the density of sea water and henceis equivalent to a specific gravity of about 1.04. The specific gravityof dense crystalline alumina isabout 4.0 and a packing of to cause thesuspension to flow.

amuse uniform size spheres is about 70% solid (our particles were quiteuniform in size) so therefore we have given a measure of the porosity ofthe particles which turns out to be about 55% pores by volume.

Referring now to the drawings illustrating apparatus which was used, therotating barrel was made of copper of largest diameter perpendicular tothe axis about four feet. It was rotated at about R. P. M. by a motor 11and speed reduction mechanism in a casing 12 driven from the motor shaft13 by pulleys 14 and i5 and a belt 16. 'The output end of the speedreduction mechanism was a pulley 18 driving a belt 1) driving a pulley2% on a shaft 21 projecting from a casing 23. In the casing 23 weremeshing bevel gears, not shown, one on the shaft 21 and another one on ashaft 26 to which the barrel 14]; was attached in the manner indicated.The supports are illustrated and need not be described and no oneskilled in the art needs further description of this part of theapparatus.

For spraying the creamy suspension we used a paint spray gun wellillustrated in cross section in Figure 2. Briefly this comprised a grip3@ having a paint intake channel 31 connected to a channel 33 in abarrel 34 by means of a spring pressed valve 35 opened by a trigger 36,the channel 33 being connected by an annular channel 37 to an annularchannel 38, both of the latter being in the barrel 34. A spray nozzle 40was screwed onto the front end of the barrel 34- providing an annularchannel 41 communicating with the channel 38 and with a delivery orifice42. Air under pressure entered the gun through a channel inside athreaded coupling portion 44, the channel 43 leading to a chamber 45communicating with a large bore 46 which communicated with a fine bore47 in an interior air nozzle 50 inside of the nozzle 40. The blast ofair from the nozzle 50 atomized the creamy suspension issuing throughthe orifice 42 and propelled it through the air. The flow of air wascontrolled by a valve 51 in the chamber 45, the valve 51 being on theend of a long valve stem 52 having a collar 53 in a tube 54 containing aspring 55 urging the collar and hence the stem 52 to the right. Thespring 55' would keep the valve 51 closed but the valve could be openedto any desired extent by adjusting nuts 57 on the threaded outer end 53of the stem 52. This gun is more fully described in U. S. Patent No.1,706,875 to A. H. Downs and so need not be further described herein.

Referring to Figure l, the grip 30 was clamped by a .clamp 60 on the endof a bracket 61 on the upper end of a rod 62 adjustably supported by atube stand 63 having a base 64 and screws 65 to clamp and unclamp therod 62. A hose 66 connected the channel 31 to a barrel containing thecreamy suspension and containing air under a pressure of about 75 poundsper square inch A hose 67 connected to the coupling portion 44 wasconnected to a source of air under a pressure of about 35 pounds to thesquare inch.

With regard to the firing conditions, while we find cone 16 conditionsgive particles of adequate strength and hardness for many applicationsand firing at cone 16 is not too expensive, we can fire at higher orlower temperatures. In the upper range of temperatures we are lim tedonly by the melting point of alumina (2050 C.) or in some cases by themelting point of the other oxide if other oxide is used. The higherfiring temperatures produce stronger and harder particles. On the lowside the mass of particles is saleable if merely dried (not fired atall) as in some cases the use of the particles will sinter them to someextent (when the catalytic reaction is at elevated temperatures).

Other examples of the invention are as follows:

Example 11 We proceed exactly as in Exaunple 1 only the creamysuspension is 73% by weight nickel oxide, N and 4 27% by weightsaturated solution of AlCl3'6H2O in water. After firing at cone 16 theparticles consist of porous matrix of nickel oxide and nickel aluminate.The original particle size of the nickel oxide may appropriately beabout 3-15 microns but can be larger say up to 325 grit size or smallerthan 3 microns if available.

Example III Again proceeding as in Example I, we provide a creamysuspension 56% by weight vanadium oxide, V2 03, b" weight saturatedsolution of AlCl3-6HzO in wa'er. After firing at cone 16 the particlesconsist of a porous mass of aluminum and vanadium oxides. The originalparticle size of the vanadium oxide may appropriately be about 3-15microns but can be larger say up to 325 grit size or smaller than 3microns if available.

It really is unnecessary to extend the discussion by giving an examplefor every one of the oxides of the sixty-seven, more or less, remainingmetals. As heretofore stated, an oxide of any of the metals can be usedand at room temperatures every metal has an oxide which is a solid. Ofcourse most metals have more than one oxide but any water stable solidmetal oxide can be used in combination with the aluminum chloride inthis invention. Naturally many oxides are too rare or too expensive forpractical use. As heretofore stated our particles do not have to becatalysts per se as being porous they can be used as catalyst carriers.

While the specific process described is a good one and at present weprefer this specific variety, the process can be varied. For example,instead of spraying the solution of aluminum chloride with or withoutmetal oxide into a water solution of ammonia, we can spray it into achamber containing gaseous ammonia, NHs. In this manner larger particlescan be made. In fact they can be as large as the spraying apparatus canmake them. When the solution is sprayed into the water solution ofammonia the particles, if they are to be approximate spheres, can be notsubstantially larger than 20 grit size since larger drops will flattenon hitting the liquid, forming particles of pancake shape. We preferspherical particles and at present we prefer particles no larger than 20grit size.

The product according to this invention consists of masses of roughlyspherical particles at least as fine as 20 grit size having a porosityof at least 20% and consisting of a matrix of aluminum oxide alone or incombination with the oxides the masses having a bulk specific gravitybetween 60 and pounds to the cubic foot.

While as aforesaid the particles can be merely dried and not fired atall, we prefer to fire the particles and we prefer to fire them under atleast cone 12 conditions.

It will thus be seen that there has been provided by this inventionaluminum oxide catalyst carrying material and a process of making thesame according to which the various objects hereinabove set forthtogether with many thoroughly practical advantages are successfullyachieved. As many possible embodiments may be made of the aboveinvention and as many changes might be made in the embodiments above setforth, it is to be understood that all matter hereinbefore set forth orshown in the accompanying drawings is to be interpreted as illustrativeand not in a limiting sense.

We claim:

1. Process for the manufacture of masses of roughly spherical particlescomprising mixing aluminum chloride solution in water with enough waterstable metal oxide powder to form a creamy suspension and then sprayingthis suspension into ammonia water, thereafter collecting and drying theparticles so produced.

2. Process according to claim 1 in which the dried particles are firedunder at least cone 12 conditions.

3. Process according to claim 2 in which the amount of metal oxidepowder is from 20% to 65% by weight 5 of the total metal oxide powderand solution calculated as saturated of AlCl3-6H20.

4. Process according to claim 3 in which the water stable metal oxidepowder is aluminum oxide.

5. Process according to-claim 1 in which the amount of metal oxidepowder is from 20% to 65% by weight of the total metal oxide powder andsolution calculated as saturated of AlCla' 6H2O.

6. Process according to claim 5 in which the water stable metal oxidepowder is aluminum oxide.

7. Process according to claim 1 in which the Water stable metal oxidepowder is aluminum oxide.

8. Process according to claim 7 in which the dried particles are firedunder at least cone 12 conditions.

References Cited in the file of this patent UNITED STATES PATENTS 61,682,241 Patrick Aug. 28, 1928 1,287,022 Burk June 23, 1932 1,871,793I-Iorsfield Aug. 16, 1932 1,935,176 Connolly Nov. 14, 1933 2,246,900Schulze June 24, 1941 2,249,767 Kistler July 22, 1941 2,273,338 ThomasFeb. 17, 1942 2,296,406 Spicer June 22, 1942 2,450,394 Brown Sept.28,1948 2,479,110 Haensel Aug. 16, 1949 2,488,150 Walden Nov. 15, 19492,492,808 Marisic Dec. 27, 1949 OTHER REFERENCES Smith: InorganicChemistry, Appleton-Century Co., N. Y., 1937, page 771.

Thorpe: Dictionary of Applied Chemistry, vol. 1, page 284, fourthedition, vol. 1, Longmans, Green and Co., N. Y., September 1941.

1. PROCESS FOR THE MANUFACTURE OF MASSES OF ROUGHLY SPHERICAL PARTICLESCOMPRISING MIXING ALUMINUM CHLORIDE SOLUTION IN WATER WITH ENOUGH WATERSTABLE METAL OXIDE POWDER TO FORM A CREAMY SUSPENSION AND THEN SPRAYING